Site-specific evaluation of safety issues for high-level waste disposal in crystalline rocks. Final report

In the past, German research and development (R and D) activities regarding the disposal of radioactive waste, including spent nuclear fuel, focused mainly on domal rock salt because rock salt was the preferred host rock formation. In addition, generic R and D work regarding alternative host rocks (crystalline rocks and claystones) had been performed as well for a long time but with lower intensity. Around the year 2000, as a consequence of the moratorium on the Gorleben site, the Federal Government decided to have argillaceous rocks and crystalline rocks investigated in more detail. As Germany does not have any underground research and host rock characterization facilities, international cooperation received a high priority in the German R and D programme for high-level waste (HLW) disposal in order to increase the knowledge regarding alternative host rocks. Major cornerstones of the cooperation are joint projects and experiments conducted especially in underground research laboratories (URL) in crystalline rocks at the Grimsel Test Site (Switzerland) and the Hard Rock Laboratory (HRL) Aespoe(Sweden) and in argillaceous rocks at the URL Mont Terri (Switzerland) and Bure (France). In 2001, the topic of radioactive waste disposal was integrated into the agreement between the former Russian Ministry of Atomic Energy (Minatom, now Rosatom) and the German Ministry of Labor (BMWA), now Ministry of Economic Affairs and Energy (BMWi), on cooperation regarding R and D on the peaceful utilization of nuclear power (agreement on ''Wirtschaftlich-Technische Zusammenarbeit'' WTZ). The intention was to have a new and interesting opportunity for international R and D cooperation regarding HLW disposal in crystalline rocks and the unique possibility to perform site-specific work, to test the safety demonstration tools available, and to expand the knowledge to all aspects specific to these host rocks. Another motivation for joining this cooperation was the intent to assist Russian engineers and scientists in their integration into the international scientific community concerned with radioactive waste disposal and to share advanced safety approaches. The corresponding joint R and D activities were pooled in the following three R and D BMWi-funded projects: - ASTER ''Requirements for Site Investigation for a HLW Repository in hard rock Formations'' (2002 - 05), to develop a well-justified methodological approach for site investigation and selection in the Nizhnekansk granitoid formation near Krasnoyarsk, exemplarily for the disposal of conditioned HLW sludge from formerly produced weapons-grade plutonium and vitrified HLW from reprocessing - WIBASTA ''Performance investigation of engineered and geologic barriers of a HLW repository in magmatic host rocks'' (2005 - 08): performance analysis of the system of geologic and engineered barriers based on safety functions, exemplarily for the proposed HLW disposal facility at the Yeniseysky site - URSEL ''Site-specific evaluation of safety issues for HLW disposal in crystalline rocks'' (2008 - 16) Main Objective: Investigation of the robustness of the safety and of the safety assessment of e repository in crystalline rocks. In the last decade of the 20th century, site investigation activities started in various preselected regions of the Nizhnekansky granitoid formation east of Krasnoyarsk. Starting in 2003, preference was given to the Yeniseysky site, which is located several kilometres south east of the underground former production facilities for weapons-grade plutonium of the Mining Chemical Combine (MCC) at Zheleznogorsk. In the beginning, these investigations were performed for the eventual disposal of conditioned HLW sludge from weapons-grade plutonium production and vitrified HLW from reprocessing of the planned reprocessing plant RT-2 at Zheleznogorsk. Recently, priority has been given to so-called class 1 waste (HLW) of the existing reprocessing plant RT-1 in Mayak and other so-called class 2 waste; i.e. long-lived radioactive waste that according to the latest IAEA1 recommendations for waste classification is called intermediate level waste (ILW). This report provides a condensed overview of the corresponding manifold site-specific safety investigations regarding HLW disposal in crystalline host rocks. The investigations were carried out by BGR, GRS, and DBE TECHNOLOGY GmbH in the last years in close cooperation with VNIPI PT and other Russian organizations involved in the investigation of the Yeniseysky site near Zheleznogorsk in the Krasnoyarsk region. The next two chapters summarize the state of knowledge available regarding the characterization of the considered site Yeniseysky and regarding the characterization of the relevant host rocks. They are followed in chapter 4 by an overview of the waste data available and in chapter 5 by a description of the most current repository concept. The evaluation of the barrier performance in chapter 6 as core part of the safety investigations performed is divided into three parts: The performance of the geotechnical and technical barriers, the performance of the geologic barrier, and the sensitivity analysis. A brief summary of the investigation results and recommendations for necessary future investigations are provided in the concluding chapter 7.